Levels excited in73Ge by (d,p) and (p,p′) reactions

Angular distributions from the reactions⁷²Ge(d, p)⁷³Ge and⁷³Ge(p, p′)⁷³Ge have been studied with 8.0 MeV deuterons and 12.0 MeV protons, respectively, using the Aldermaston Tandem Van de Graaff generator and multi-angle magnetic spectrograph. The ground stateQ-value of the (d, p) reaction was measured to be 4.571±0.004 MeV. The energies, values of the transferred orbital angular momenta, parities and transition strengths in both reactions were determined by use of distorted-wave Bornapproximation calculations, for levels up to 3 MeV excitation energy. The sums of the transition strengths are compared with shell model calculations as well as with values obtained in neighbouring nuclei. Discrepancies between parity and possible spin assignments of states observed in the two reactions are discussed.     

Direct currents generated by microwave heating in toroidal plasma

The existence of a direct toroidal current in a magnetized plasma torus heated by microwaves is established experimentally. The dependences of that electric current on microwave power and gas pressure are given. The experimental results are consistent with the theory of non-linear dragging of electrons by waves travelling along the torus.     

Ozonides,epoxides, and oxidoannulenes of C(70)

Six new monoadducts of C(70) with oxygen species have been prepared, isolated, and characterized following ozonation of C(70) solutions. The initial products are two ozonide monoadducts, identified as a,b- and c,c-C(70)O(3). These ozonides lose O(2) through thermolysis or photolysis to form various isomers of C(70)O. The a,b-C(70)O(3) isomer dissociates through thermolysis with a decay time of 14 min at 296 K to form the [6,6]-closed epoxide a,b-C(70)O. When photolyzed, it instead forms a [5,6]-open oxidoannulene identified as a,a-C(70)O. These reactions mimic those seen for C(60)O(3). By contrast, the c,c-C(70)O(3) isomer, which has a thermolysis lifetime of 650 min at 296 K, decays thermally only to an oxidoannulene deduced to be d,d-C(70)O. Photolysis of c,c-C(70)O(3) produces a mixture of the oxidoannulenes b,c-C(70)O and c,d-C(70)O plus a minor amount of the c,c-epoxide. All four C(70)O oxidoannulene isomers undergo photoisomerization, giving eventually the a,b- and c,c-C(70)O epoxides.     

Trivelpiece-Gould-Modes in an Axial Inhomogeneous Plasma

Experiments on the propagation of TG-modes in a weakly inhomogeneous plasma are reported. The modes travel from the high density part (ω < ω_pe) to that of lower density (ω > ω_pe). The wavelength decreases as expected but an increase of the longitudinal fieldstrength predicted by collisionless theory could not be observed. Two nonlinear effects appear one after another with increasing wave amplitude. These are the sideband instability and a decay into the drift frequency range occuring in the whole plasma column. Neither the region ω ≈ ω_pe nor the very vicinity of the exciter antenna are distinguished. The second instability is accompanied by effective electron heating.     

Transmission of sound through pipe walls in the presence of flow

The transmission of sound through pipe walls was studied experimentally under no-flow conditions as well as with steady air flow velocities up to 120 m/s. The test specimens were commercial pipe and tube of diameter ranging from 0·07 to 0·3 m, and thickness-to-diameter ratios from 0·12 to 0·2. The technique involved two reverberant rooms, one traversed by the test pipe to measure externally radiated sound, and one in which the test pipe terminated to measure internally propagated sound. Vibration of the pipe wall was also monitored to determine radiation efficiency.The results show that no-flow transmission loss (TL) is higher than predicted by available theoretical expressions, but that TL decreases strongly with increasing flow velocity. A qualitative explanation for the latter is offered. Radiation efficiency was found to be independent of flow velocity. The scaling of results between “similar” specimens was moderately successful. The results are documented in sufficient detail to permit their use for forming empirical models as well as for testing future theoretical predictions.     

Evolution of time constants during sol-gel transition

In developing a rheological constitutive equation for crosslinking polymers the determination and explanation of time constants are of great importance. For stoichiometrically balanced and imbalanced reactions of polydimethylsiloxane and polyurethane model polymers with appropriate cross-linkers, it is shown that the experimental data for the storage and loss moduli are well fitted within a large frequency range by a linear rheological constitutive equation with a truncated power law relaxation function.Special attention is given to the problem of estimating the different time constants. A method is proposed for the determination of the terminal relaxation time (in the case below the gel point) and a characteristic retardation time (in the case above the gel point) from the intersection points of the high and low frequency asymptotes of the storage modulus.     

High‐Pressure Synthesis and Single‐Crystal Structure Elucidation of the Indium Oxide‐Borate In4O2B2O7

The indium oxide‐borate In₄O₂B₂O₇ was synthesized under high‐pressure/high‐temperature conditions at 12.5 GPa/1420 K using a Walker‐type multianvil apparatus. Single‐crystal X‐ray structure elucidation showed edge‐sharing OIn₄ tetrahedra and B₂O₇ units building up the oxide‐borate. It crystallizes with Z = 8 in the monoclinic space group P2₁/n (no. 14) with a = 1016.54(3), b = 964.55(3), c = 1382.66(4) pm, and β = 109.7(1)°. The compound was also characterized by powder X‐ray diffraction and vibrational spectroscopy.     

UF4 and the High-Pressure Polymorph HP-UF4

A laboratory-scale synthesis of UF₄ is presented that utilizes the reduction of UF₆ with sulfur in anhydrous hydrogen fluoride. An excess of sulfur can be removed by vacuum sublimation, yielding pure UF₄, as shown by powder X-ray diffraction, micro X-ray fluorescence analysis, infrared and Raman spectroscopy, as well as magnetic measurements. Furthermore, a single-crystalline, high-pressure modification of UF₄ was obtained in a multi-anvil press at elevated temperatures. The high-pressure polymorph HP-UF₄ was characterized by means of single-crystal and powder X-ray diffraction, as well as by magnetic measurements, and presents a novel crystal structure type. Quantum-chemical calculations show the HP-modification to be 10 kJ mol⁻¹ per formula unit higher in energy compared to UF₄.